1. Field of the Invention
The present invention relates to a lateral diffused metal-oxide-semiconductor (LDMOS) device, and more particularly, to an LDMOS device with a Schottky diode.
2. Description of the Prior Art
A lateral diffused metal-oxide-semiconductor (LDMOS) device is a kind of popular power semiconductor device. Due to having a planar structure, the LDMOS is easily manufactured and is easily integrated with semiconductor technology, so that the manufacturing cost may be reduced. The LDMOS further has higher breakdown voltage and higher output power so as to be applied in the devices, such as power converter, power amplifier, switch, and rectifier, etc.
In a traditional LDMOS device, an N-type doped drain region and a P-type doped base region are usually disposed in an n-type drift region, and an N-type doped source region is disposed in the P-type doped base region. A gate metal is disposed on the P-type doped base region between the N-type doped source region and the N-type drift region. A source metal is disposed on the N-type doped source region and the P-type doped base region, and is electrically connected to a low voltage end of a power source. A drain metal is disposed on the N-type doped drain region, and is electrically connected to a high voltage end of the power source. Furthermore, a field oxide is disposed on the N-type drift region and between the gate metal and the drain metal, and is used for tolerating high electric field from the high voltage end. As we can know that the P-type doped base region and the N-type drift region in the traditional LDMOS device form a parasitic diode.
Although the parasitic diode provides a reverse current path from source to drain in order to introduce minor charges, the area and the transferring speed of the reverse current path are too small to eliminate the reverse source current rapidly, so that an energy loss of the LDMOS device is generated when switching the LDMOS device. Thus, to eliminate the reverse source current through the parasitic diode cannot satisfy recent requirements. To raise the reverse source current of the LDMOS device is an important objective in this field.